Copper oxide rectifier



Jan. 19, 1932. H. KAHLER COPPER OXIDE RECTIFIER Filed Dec. 7, 1928 Pfm C e a us .|d.

..m a w 9 X e X .L 0 o 7 I Container Wall I r e P P 0 C d e .m H v o INVENTOR Herb rt Kahler' ATTORNEY Patented Jam I19, 1932' f HERBERT manna, or xansmerom naanm, Manon r wns'rmenousa a TRIO a MANUFACTURING COMPANY,

A. common or rnuusnvanu corrnn oxmn Application and December '2, 1m. sem 110. 824,502. 1

My invention relates to the general class of rectifiers which utilize the uni-lateral electrical conductivity of a .junction between .metal and a component thereof, and,mo re 5 particularly, my invention relates to rectifiers which utilize the uni-lateral conductlvity of a junction between copper and'an ox de thereof. A p.

An object of my invention is to provide a rectifier adapted for large current output.

Another object of my invention is to provide a rectifier adapted for large current output per unit of wei ht. l 1

A further object o my invention is to provide a rectifier in which the metal comprising the same is utilized with great efficiency.

Other objects of my invention will become evident upon reading the following specification, taken in connection with the appended drawings, in which: 1

Figure 1 is a sectional view of a rectifier Lembodyingthe principles of my invention;

' and component rectifying elements employed in the structure shown in Fig. 1.

Rectifiers which make use of the uni-lateral electrical conductivity which is found to sub-' Where currents of only the magnitude of one half ampere are desired, little attention ficient area of oxidized surface, since structural,considerations require a sufficient body of metal to provide a considerable surface area.- Howev-er, where'it is desired to obtain currents of the order of 100 amperes, the surface area of the oxide required becomes very large, and considerations of economy demand that the amount of metal necessary for providing the requlred oxide surface shall be reduced to a minimum. 1

Fig. 2 is an elevational view of one of the need be paid to the problem of obtaining suf- In accordance with the principles of my invention, the elementary copper blanks upon which the'oxide surface is produced, take the form of relatively thin plates or sheets having both surfaces oxidized. Since the re-. sistance of the oxide layer is large compared with that of metallic copper, it is economical to cover the major portion of the co per plate with oxide, a relatively small area 'eing left free ofoxide, so that electrical connections may be made with the underlying mother metal. a

In accordance with a further feature of m invention, the copper sheets are oxidized s1- multaneously on both sides by heating them .in contact with the air, a small area of surface being kept covered to revent its oxidation and to thereby provi e the necessary small contact area forconnection to the underlying metal. By the expedient of oxidizing the two opposite sides of a late or sheet simultaneously, it is prevented rom warping and bending out of shape, as it is found to do when onl one side is, oxidized at a time.

With the oregoing principlesand objects in mind, reference may be had to Fig. 1' of the drawings in which copper plates, which form the principal elements of the rectifier, have substantially all of'their op osite faces covered by layers 2 of oxide. As 1s indicated in the detail yiew in Fig. 2, a small area 3 is left free from oxide on one or both sides of the plates 1.

vWhen assembled in the complete rectifier, a sheet of lead 4 is so positioned as to cover both faces of the plates 1 except in the immediate vicinity of the areas 3. If desired, the surface of the oxide layer may first be covered with. finely powdered graphite to insure better contact with the lead sheets.

A unit comprising an oxidized copper plate 1 and its sheet-lead covering 4 constitutes an elementary rectifier, itbeing found that electrons .flow freely from the co per to the oxidized layer and thence to the end sheath but practically not at all in the reverse direction. Accordingly,.if an alternating voltage is impressed between the underlying copper'of the sheet and the lead sheath, current passes substantially only in one direction,

I no

uni-directional current flow thus resulting. In accordance with well-known electrical connections, a plurality of elementary rectifier units of the kind just described may be as sembled to pass both half cycles of alternating current and so provide a direct-current output.

In accordance with the foregoing, any desired number of elementary rectifier units of the type above described may be assembled side-by-side with their lead sheaths in contact. In one convenient form of structure, the unoxidized portions 3 are made to align and are drilled to receive a through-bolt 5. Copper spacing washers 6 of suitable thickness, approximately equal to twice that of the lead sheath enclosing the plates, are fitted over the. through-bolts between the rectifier plates. An assembly of the desired number of rectifier units may then be put in place betweenthe walls of a container 7 adapted to make electrical contact with the exterior of the lead sheaths 4. The container 7 may, if desired, be provided with suitable tension bolts to draw its end-walls into firm contact with the sheaths 4. Terminal connections for line wires 8 and 9 may then be bolted in place, respectively, on the through-bolts 6 and to the container 7. i w

The oxidized copper plates 1 may conveniently be produced in the following way:

A clean copper plate of the desired surface area and preferably havinga very large ratio of surface to volume may be heated in air to a temperature varying between 500 degrees centigrade and the melting point of copper, the precise temperature depending upon the particular electrical characteristics of the rectifier desired. For most purposes, I have found that heating to a temperature'of 1040 degrees centigrade for a period in the neighborhood of one-half an hour produces desirable results, although, as above stated, heating to other temperatures below the melting point of copper is within the purview of my invention. In my preferred process, the copper plate is cooled, in the course of some five minutes, to 700 degrees centigrade.- The plate is then removed from the furnace and cooled rapidly in air.

, In orderto maintain the areas 3 free from oxide, they may be covered by copper clamps of the desired area which will efi'ectively exclude the air from contact with them and thereby prevent their oxidation.

For some purposes, it may be desirable to provide an oxidized area on only one side of the copper pJIate, in which case, oxidation thereof may e prevented by merely laying a copper blank of suitable size on the upper facing of the plate 1, while subjecting the latter to the heating and oxidizing process above described.

While the foregoing method of producing contact areas free from oxide is desirable,

it will be understood to be still within the purview of my invention to oxidize the entire surface of the plate and then to free the necessary contact areas by removal or reduction of the oxide over the desired area. It will also be recognized that, while I have described the principles of my invention as applied to ox'idized copper rectifiers they are broadly applicable to other compounds of copper and also to compounds of other metals suitable for the formation of contact rectifiers. Ways will readly be evident to persons skilled in the art by which the principles of my invention may be applied with many other structural embodiments than those which I have specifically described in the foregoing. I desire, therefore, that the claims be limited only in accordance with their express terms and by the prior art.

I claim as my invention:

1. A contact rectifier comprising a metallic plate having its sides and edges oxidized except for a relatively small area on one or both of its sides, means for making electrical contact with the greater part of said small area and means for making electrical contact with said oxidized surface.

2. A contact rectifier comprising a plurality of metallic plates, each plate being oxidized on both sides except for a small area on one or both sides thereof, said plates being so stacked that. adjacent oxidized areas are in' electrical contact with each other and said small areas are in electrical contact with each other, means for connecting'said oxidized areas to one terminal and means for connecting said small areas to a second terminal.

3. A contact rectifier comprising a metallic plate oxidized on the edges and on each side except for a relatively small area, a terminal member in electrical contact with the greater part of said small area, and means for making good electrical contact with the greater part of said oxidized surface on each side of said plate, said means being con nected to a second terminal.

4. A contact rectifier comprising a plurality of metallic plates, each plate completely oxidized on both sides except for a small area, saidplates being placed adjacent to each other with a sheet of relatively soft.

connecting material between said plates which is in contact with the oxidized surface only of said plates, said small areas belng held in good electrical contact with each,

electrical contact with each other and connected to a terminal, and a metallic casing enclosing said units and acting as a conductor to connect a secondtermin'al to said oxidized surfaces; 7

6.-' A contact rectifierconsisting of a plurality of units, each unit comprising a metallic plate oxidized on both sides except for I a small area on at least one side thereof, a conducting layer which electrically connects the oxidized surfaces on opposite sides of said plate, said units being so placed in contact with each other that the conducting layer of one unit makes contact with the conducing layer of another unit, said small areas being held in good electrical contact with each other.

,7. A contact rectifier consisting of a plurality of units, each unit comprising a metallic plate completely oxidized except for a small area on, at leastv one side thereof, a

, single sheet of soft conducting material extending from one side of said plate around one oxidized edge to the other side .ofsaid plate and being in contact with the oxide 7 layer only on said plate, said units being so placed in contact with each other that the soft conducting material of one unit makes contact with the soft conducting'material of another unit.

In testimony whereof, I

" HERBERT KAHLER.

have hereunto subscribed my name this 30th day of November, 

